As previously mentioned, the disorders in the OCRDs category have both similarities and differences. Although all the disorders in this category have intrusive thoughts, these obsessional thoughts manifest somewhat differently. Some disorders, such as obsessive-compulsive disorder (OCD) are characterized by classic obsessions. Obsessions are repetitive, unwanted, and intrusive thoughts that trigger anxiety. In other disorders, such as BDD and hoarding disorder, the intrusive thoughts could be more aptly described as a persistent and unrelenting preoccupation. In the case of BDD, this preoccupation focuses on personal appearance and attractiveness. In the case of hoarding disorder, the preoccupation centers around possessions.
The intrusive thoughts of people with hoarding disorder are associated with their preoccupation regarding their possessions; specifically, parting with, or losing these possessions. Unlike spontaneous OCD obsessions, intrusive hoarding thoughts and resultant anxiety are not usually activated until faced with the prospect of losing or parting with possessions.
People also report intrusive and repetitive thoughts surrounding the "need" to acquire a possession, and experience anxiety until that object is acquired. Ordinary, everyday situations can trigger someone's obsessional desire to acquire something (i.e., a free promotional give-away, a newspaper advertisement, etc.). Moreover, individuals with hoarding often describe their acquisition behavior as a compulsion, experienced as strong urges. They feel driven to acquire the desired items and experience significant anxiety if they do not. A difference between OCD and hoarding disorder is that in hoarding disorder the compulsive acquisition of items results in a "pleasurable" feeling. This is not the case for compulsions in OCD.
Like OCD and BDD, hoarding disorder has an insight specifier to further refine the diagnosis. While it is true that obsessions and compulsions are based on inaccurate or irrational beliefs, people differ in terms of whether they recognize this fact. In other words, some people readily recognize and accept their obsessions are not sensible. Nonetheless, this insight is insufficient to prevent the obsessions and compulsions. Other people lack this insight. They firmly cling to their distorted beliefs, despite evidence that refutes the validity of such beliefs. This lack of insight is important with respect to treatment. In general, people with poor or absent insight have a poorer prognosis for a full and complete recovery.
There are three insight specifiers: 1) good/fair, 2) poor, or 3) absent/delusional. An insight specifier rates a person's degree of insight about their disorder-related beliefs. With respect to hoarding disorder, the insight specifier indicates how fixed or rigid the disorder-related beliefs are. It also indicates whether or not someone understands their beliefs and behaviors are problematic. Of note, animal hoarding is associated with poorer insight.
Unlike people with OCD, people with hoarding disorder may interpret their disorder-related beliefs and behaviors as sensible ideas that reflect their overall value system. For instance, many people value the importance of being thrifty and avoiding wastefulness. If such a person develops a hoarding disorder, they may interpret their hoarding behavior as sensible and consistent with the need to be thrifty and avoid wastefulness. Therefore, as with BDD, insight into the nature of their problem is often a significant treatment obstacle. This is because people are not motivated to "fix" something that does not strike them as problematic.
It is often difficult for an outside observer to understand how people with a hoarding disorder do not grasp the severity or magnitude of the problem. One reason for this difficulty is they often minimize the harmful impact to themselves, or to their loved ones. People with particularly poor insight often shift the blame for the problem to others, or attempt to rationalize the reasons for the problem (i.e., but not their problem). Therefore, traditional cognitive-behavioral treatments need to be modified. Like BDD, treatment may need to include cognitive restructuring of dysfunctional and inaccurate beliefs. Motivation for change may need to be developed or strengthened before treatment can proceed.
Treatment for hoarding disorder does not usually progress as smoothly or quickly as treatment for OCD. Notwithstanding these differences, there is often a higher comorbidity rate between OCD and hoarding disorder as compared to other mental disorders. Like OCD, there is also evidence of a familial link.